The present invention relates to a progressive suspension device for the rear wheel of a motorcycle. The progressive, rear-wheel suspension device according to the present invention comprises a swinging fork for a wheel acting on a single damping spring assembly through at least one connecting rod and one rocker.
Rear-wheel suspension devices of this type are known, for example, from U.S. Pat. No. 4,076,271.
The U.S. patent describes a vehicle wheel suspension device for the rear wheel of a motorcycle. In one embodiment of it, this prior art suspension device comprises a fork for a rear wheel and two rods connected at the end of the fork close to the wheel in such a way as to transfer the force applied by the wheel on the fork to a single spring and damper through an intermediate swing element. The rods transmit only axial type forces and are arranged in such a way as to form the edges of a pyramid with downward pointing apex. In another embodiment of the invention, the fork has a reticulate structure whose elements are subjected mainly to normal forces.
Although the suspension device of the patent just described discloses solutions, such as the single spring and dampers, which make it possible to reduce overall dimensions, it is difficult to construct because it is based on unsubstantial components which, if they are to be subjected to only axial forces, must be constructed with extremely high dimensional and assembly precision. Further, the suspension device is difficult to adjust in terms of the ratio of force to wheel movement and is also unsuitable for a suspension device consisting of a fork with a single swing arm.
The present invention has for one of its objects to provide an improved progressive suspension device for the rear wheel of a motorcycle that may be applied to forks with either one or two arms, that may be easily adjusted in terms of the ratio of force to wheel movement, and that is easy to adapt to the constructional tolerances of the motorcycle to which it has to be fitted.
Another object of the present invention is to provide a rear-wheel suspension device that is economical, compact and occupies parts of the motorcycle that are not normally used.
In accordance with one aspect of it, the present invention discloses a progressive suspension device for the rear wheel of a motorcycle as described in the independent claim below. The dependent claims describe preferred, advantageous embodiments of the invention.